Chem 101 Book Answers (Ch.2)

Chem 101 Book Answers (Ch.2) - Chapter 2 Quantum Theory 1....

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Chapter 2 Quantum Theory 1. Which has more energy, a photon of microwave radiation or a photon of infrared radiation? Infrared radiation has a shorter wavelength and a higher frequency than microwave radiation (Figure 2.2). Consequently, infrared photons are more energetic than microwave photons. 3. Radiation from the sun can cause the decomposition of O 2 in the stratosphere: O 2 2O. This requires 495 kJ/mol of energy. What is the longest wavelength of light in nm that can accomplish this process? In what region of the electromagnetic spectrum ( i.e. , infrared, visible, ultraviolet, etc.) is light of this energy found? E = 4.95 × 10 5 J mol × 1 mol 6.02 × 10 23 photon = 7.72 × 10 19 J/photon We obtain the frequency of a photon with this energy from Equation 2.1 ν = -19 15 -1 -34 E 7.72×10 J/photon = = 1.17×10 s h 6.63×10 J×s The wavelength of light with this frequency is λ = c ν = 3.00 × 10 8 m s -1 1.17 × 10 15 s -1 = 2.56 × 10 7 m = 256 nm a UV (ultraviolet) photon 5. Fill in the following table: λ (nm) ν (s -1 ) E/photon (J) E/mol photons (kJ/mol) 333 9.00 x 10 14 5.97 x 10 -19 360 47 6.42 x 10 15 4.25 x 10 -18 2.56 x 10 3 107 2.81 x 10 15 1.86 x 10 -18 1.12 x 10 3 1.11 x 10 3 2.71 x 10 1.79 x 10 108 7. Use the Bohr model to determine the radii of the n = 2 and n = 4 orbits of a He 1+ ion. Use Equation 2.4 and Z = 2: ⎛⎞ ⎜⎟ ⎝⎠ 2 -11 -11 2 2 -11 -10 4 2 r = 5.292×10 = 1.058×10 meters = 10.58 pm 2 4 = 4.236×10 meters = 423.6 pm 2 9. Determine the energies of the n = 2 and n = 3 levels of a He 1+ ion. What region of the spectrum ( i.e ., infrared, visible, ultraviolet, etc.) would the n = 3 2 transition in He 1+ ion occur? Is this transition an absorption or an emission?
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This note was uploaded on 10/30/2009 for the course CH Ch101 taught by Professor Bigham during the Fall '08 term at N.C. State.

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Chem 101 Book Answers (Ch.2) - Chapter 2 Quantum Theory 1....

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